SUMMARY
Updating from 6.0.3 to 6.0.4 causes every application running using the Vulkan API to run at extremely low (~5fps) framerates.

STEPS TO REPRODUCE
0. With every package already updated to 6.0.4, except extra/kwayland extra/kwayland-integration extra/kwin still on 6.0.3
1. Start a game like StardewValley, or Stellaris which runs under Vulkan
2. Notice that the game runs fluidly, and animations are fluid
3. Update those remaining packages to 6.0.4
4. Run the same game again

OBSERVED RESULT
Animations are jagged, and the game is clearly running at a very low framerate. Low enough for even the mouse movement to be noticably laggy making the whole experience unbarable.

EXPECTED RESULT
There should be no performance regression.

SOFTWARE/OS VERSIONS
Operating System: Garuda Linux 
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.1.0
Qt Version: 6.7.0
Kernel Version: 6.8.7-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 32 × AMD Ryzen 9 7950X 16-Core Processor
Memory: 61.9 GiB of RAM
Graphics Processor: AMD Radeon RX 7900 XTX
Manufacturer: ASUS

I am still running mesa 24.0.3-1, since updating to any more recent version on my system causes kwin to crash with a memory alignment error in radeonsi. See https://gitlab.freedesktop.org/mesa/mesa/-/issues/10839

ADDITIONAL INFORMATION
You can verify that this only impacts the Vulkan API, since apps using the OpenGL API, like the plasma desktop, or Unigine Superposition still behave correctly.

While the instructions mentions to leave all wayland packages to 6.0.3, I haven't tested updating those specifically to pinpoint the bug to kwin since I assumed they were all somewhat tied together.